Carboxyl-terminal domain III of the delta' subunit of DNA polymerase III holoenzyme binds DnaX and supports cooperative DnaX complex assembly

J Biol Chem. 2001 Dec 28;276(52):48709-15. doi: 10.1074/jbc.M107936200. Epub 2001 Oct 17.


The delta' subunit of the DNA polymerase-III holoenzyme is a key component of the DnaX complex; it is required for loading the beta(2) processivity factor onto a primed template. The x-ray crystal structure of delta' indicates a three domain C-shaped structure (Guenther, B., Onrust, R., Sali, A., O'Donnell, M., and Kuriyan, J. (1997) Cell 91, 335-345). In this study, we localized the DnaX-binding domain of delta' to its carboxyl-terminal domain III by quantifying protein-protein interactions using a series of delta' fusion proteins lacking specific domains. The fusion protein corresponding to domain III of delta' bound to DnaX with an affinity approaching that of full-length delta'. In contrast, a construct bearing delta' domains I-II did not bind DnaX at detectable levels. The presence of delta and chi psi strengthened the interaction of DnaX with full-length delta' and delta' domain III. Thus, domain III of delta' not only contains the DnaX-binding site, but also contains the elements required for positive cooperative assembly of the DnaX complex. A domain III-specific anti-delta' monoclonal antibody interfered with DnaX complex formation and abolished the replication activity of DNA polymerase III holoenzyme.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Monoclonal / metabolism
  • Bacterial Proteins / metabolism*
  • DNA Polymerase III / chemistry
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • Macromolecular Substances
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Subunits
  • Recombinant Fusion Proteins / metabolism


  • Antibodies, Monoclonal
  • Bacterial Proteins
  • DnaX protein, Bacteria
  • Macromolecular Substances
  • Protein Subunits
  • Recombinant Fusion Proteins
  • DNA Polymerase III